1. Field of the Invention
This invention relates generally to oilfield operations and more particularly to systems and methods utilizing fiber optics for monitoring wellbore parameters, formation parameters, drilling operations, condition of downhole tools installed in the wellbores or used for drilling such wellbores, for monitoring reservoirs and for monitoring of remedial work.
2. Background of the Art
A variety of techniques have been utilized for monitoring reservoir conditions, estimation and quantities of hydrocarbons (oil and gas) in earth formations, for determination formation and wellbore parameters and form determining the operating or physical condition of downhole tools.
Reservoir monitoring typically involves determining certain downhole parameters in producing wellbores, such as temperature and pressure placed at various locations in the producing wellbore, frequently over extended time periods. Wireline tools are most commonly utilized to obtain such measurements, which involves shutting down the production for extended time periods to determine pressure and temperature gradients over time.
Seismic methods wherein a plurality of sensors are placed on the earth's surface and a source placed at the surface or downhole are utilized to obtain seismic data which is then used to update prior three dimensional (3-D") seismic maps. Three dimensional maps updated over time are sometimes referred to as "4-D" seismic maps. The 4-D maps provide useful information about reservoirs and subsurface structure. These seismic methods are very expensive. The wireline methods are utilized at great time intervals, thereby not providing continuous information about the wellbore conditions or that of the surrounding formations.
Permanent sensors, such as temperature sensors, pressure sensors, accelerometers or hydrophones have been placed in the wellbores to obtain continuous information for monitoring wellbores and the reservoir. Typically, a separate sensor is utilized for each type of parameter to be determined. To obtain such measurements from useful segments of each wellbore, which may contain multilateral wellbores, requires using a large number of sensors, which require a large amount of power, data acquisition equipment and relatively large amount of space, which in many cases is impractical or cost prohibitive.
In production wells, chemicals are often injected downhole to treat the producing fluids. However, it can be difficult to monitor and control such chemical injection in real time. Similarly, chemicals are typically used at the surface to treat the produced hydrocarbons (i.e. break down emulsions) and to inhibit corrosion. However, it can be difficult to monitor and control such treatment in real time.
Formation parameters are most commonly measured by measurement-while-drilling tools during the drilling of the wellbores and by wireline methods after the wellbores have been drilled. The conventional formation evaluation sensors are complex and large in size and thus require large tools. Additionally such sensors are very expensive.
Prior art is also very deficient in providing suitable system and methods for monitoring the condition or health of downhole tools. Tool conditions should be monitored during the drilling process, as the tools are deployed in the wellbore and after deployment, whether during the completion phase or the production phase.
The present invention addresses some of the above-described prior deficiencies and provides systems and methods which utilize a variety of fiber optic sensors for monitoring wellbore parameters, formation parameters, drilling operations, condition of downhole tools installed in the wellbores or used for drilling such wellbores, for monitoring reservoirs and for monitoring of remedial work. In some applications, the same sensor is configured to provide more than one measurement. in many instances these sensors are relatively, consume less power and can operate at higher temperatures than the conventional sensors.